1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
2. Description of the Related Art
For manufacturing semiconductor devices exemplified by diodes, integrated circuits (ICs) and the like, processes for connecting chip-like semiconductor devices, which are diced into a predetermined size from a wafer, to a fixing member such as a lead frame by soldering and the like, and then firmly adhering electrode layers, which are formed on upper surfaces of such semiconductor chips, and electrode terminals of the lead frame to each other by wire bonding, are executed.
In an event of wire bonding a metallic wire and a surface of a metallic electrode layer by bringing the metallic wire in contact with the metallic electrode layer, a damage such as a crack sometimes occurs in the electrode layer owing to power of ultrasonic waves. As a technology for suppressing such a wire bonding damage, there is proposed a method of adopting a double-layer structure for an interlayer insulating film to be formed under the electrode layer of the semiconductor device, and forming irregular portions between the upper and lower films of the double-layer structure, and thereby reducing the damage at a time of the wire bonding (refer to JP2005-303186A).
However, in semiconductor devices such as a metal-oxide-semiconductor field-effect transistor (MOSFET) and an insulated gate bipolar transistor (IGBT), which are used, for example, as power semiconductor devices, a relatively large current flows between the semiconductor device and an outside, and accordingly, it is necessary to increase a diameter of the wire for the bonding (for example, to approximately 300 micrometers). Moreover, a thickness of the electrode layer of the power semiconductor device approximately ranges from one to ten micrometers in usual, and accordingly, the diameter of the wire becomes much larger than the thickness of the electrode layer. Therefore, a load to the electrode layer by the wire bonding also becomes large, and accordingly, the damage such as the crack, which occurs in the semiconductor device, cannot be sufficiently reduced in some case even if the technology of JP2005-303186A is used. Then, among a variety of characteristics of the semiconductor device, which are deteriorated by the damage, in particular, a deterioration of a gate threshold voltage of the semiconductor device, which is caused by an influence of impurities such as movable ions contained in a package, is significant, and a method for solving the deterioration of the gate threshold voltage has been desired.